//******************************************************************************
//
// File:    SharedDouble.java
// Package: edu.rit.pj.reduction
// Unit:    Class edu.rit.pj.reduction.SharedDouble
//
// This Java source file is copyright (C) 2007 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************

package edu.rit.pj.reduction;

import java.util.concurrent.atomic.AtomicLong;

/**
 * Class SharedDouble provides a reduction variable for a value of type
 * <TT>double</TT>.
 * <P>
 * Class SharedDouble is multiple thread safe. The methods use lock-free atomic
 * compare-and-set.
 * <P>
 * <I>Note:</I> Class SharedDouble is implemented using class
 * java.util.concurrent.atomic.AtomicLong. The double value is stored as a
 * <TT>long</TT> whose bit pattern is the same as the double value.
 *
 * @author  Alan Kaminsky
 * @version 07-Jun-2007
 */
public class SharedDouble
	extends Number
	{

// Hidden data members.

	private AtomicLong myValue;

// Exported constructors.

	/**
	 * Construct a new double reduction variable with the initial value 0.
	 */
	public SharedDouble()
		{
		myValue = new AtomicLong (Double.doubleToLongBits (0.0));
		}

	/**
	 * Construct a new double reduction variable with the given initial value.
	 *
	 * @param  initialValue  Initial value.
	 */
	public SharedDouble
		(double initialValue)
		{
		myValue = new AtomicLong (Double.doubleToLongBits (initialValue));
		}

// Exported operations.

	/**
	 * Returns this reduction variable's current value.
	 *
	 * @return  Current value.
	 */
	public double get()
		{
		return Double.longBitsToDouble (myValue.get());
		}

	/**
	 * Set this reduction variable to the given value.
	 *
	 * @param  value  New value.
	 */
	public void set
		(double value)
		{
		myValue.set (Double.doubleToLongBits (value));
		}

	/**
	 * Set this reduction variable to the given value and return the previous
	 * value.
	 *
	 * @param  value  New value.
	 *
	 * @return  Previous value.
	 */
	public double getAndSet
		(double value)
		{
		return Double.longBitsToDouble
			(myValue.getAndSet (Double.doubleToLongBits (value)));
		}

	/**
	 * Atomically set this reduction variable to the given updated value if the
	 * current value equals the expected value.
	 *
	 * @param  expect  Expected value.
	 * @param  update  Updated value.
	 *
	 * @return  True if the update happened, false otherwise.
	 */
	public boolean compareAndSet
		(double expect,
		 double update)
		{
		return myValue.compareAndSet
			(Double.doubleToLongBits (expect), Double.doubleToLongBits (update));
		}

	/**
	 * Atomically set this reduction variable to the given updated value if the
	 * current value equals the expected value. May fail spuriously.
	 *
	 * @param  expect  Expected value.
	 * @param  update  Updated value.
	 *
	 * @return  True if the update happened, false otherwise.
	 */
	public boolean weakCompareAndSet
		(double expect,
		 double update)
		{
		return myValue.weakCompareAndSet
			(Double.doubleToLongBits (expect), Double.doubleToLongBits (update));
		}

	/**
	 * Add one to this reduction variable and return the previous value.
	 *
	 * @return  Previous value.
	 */
	public double getAndIncrement()
		{
		for (;;)
			{
			long oldvalueLong = myValue.get();
			double oldvalue = Double.longBitsToDouble (oldvalueLong);
			double newvalue = oldvalue + 1.0;
			long newvalueLong = Double.doubleToLongBits (newvalue);
			if (myValue.compareAndSet (oldvalueLong, newvalueLong))
				{
				return oldvalue;
				}
			}
		}

	/**
	 * Subtract one from this reduction variable and return the previous value.
	 *
	 * @return  Previous value.
	 */
	public double getAndDecrement()
		{
		for (;;)
			{
			long oldvalueLong = myValue.get();
			double oldvalue = Double.longBitsToDouble (oldvalueLong);
			double newvalue = oldvalue - 1.0;
			long newvalueLong = Double.doubleToLongBits (newvalue);
			if (myValue.compareAndSet (oldvalueLong, newvalueLong))
				{
				return oldvalue;
				}
			}
		}

	/**
	 * Add the given value to this reduction variable and return the previous
	 * value.
	 *
	 * @param  value  Value to add.
	 *
	 * @return  Previous value.
	 */
	public double getAndAdd
		(double value)
		{
		for (;;)
			{
			long oldvalueLong = myValue.get();
			double oldvalue = Double.longBitsToDouble (oldvalueLong);
			double newvalue = oldvalue + value;
			long newvalueLong = Double.doubleToLongBits (newvalue);
			if (myValue.compareAndSet (oldvalueLong, newvalueLong))
				{
				return oldvalue;
				}
			}
		}

	/**
	 * Add one to this reduction variable and return the new value.
	 *
	 * @return  New value.
	 */
	public double incrementAndGet()
		{
		for (;;)
			{
			long oldvalueLong = myValue.get();
			double oldvalue = Double.longBitsToDouble (oldvalueLong);
			double newvalue = oldvalue + 1.0;
			long newvalueLong = Double.doubleToLongBits (newvalue);
			if (myValue.compareAndSet (oldvalueLong, newvalueLong))
				{
				return newvalue;
				}
			}
		}

	/**
	 * Subtract one from this reduction variable and return the new value.
	 *
	 * @return  New value.
	 */
	public double decrementAndGet()
		{
		for (;;)
			{
			long oldvalueLong = myValue.get();
			double oldvalue = Double.longBitsToDouble (oldvalueLong);
			double newvalue = oldvalue - 1.0;
			long newvalueLong = Double.doubleToLongBits (newvalue);
			if (myValue.compareAndSet (oldvalueLong, newvalueLong))
				{
				return newvalue;
				}
			}
		}

	/**
	 * Add the given value to this reduction variable and return the new value.
	 *
	 * @param  value  Value to add.
	 *
	 * @return  New value.
	 */
	public double addAndGet
		(double value)
		{
		for (;;)
			{
			long oldvalueLong = myValue.get();
			double oldvalue = Double.longBitsToDouble (oldvalueLong);
			double newvalue = oldvalue + value;
			long newvalueLong = Double.doubleToLongBits (newvalue);
			if (myValue.compareAndSet (oldvalueLong, newvalueLong))
				{
				return newvalue;
				}
			}
		}

	/**
	 * Combine this reduction variable with the given value using the given
	 * operation. The result is stored back into this reduction variable and is
	 * returned.
	 *
	 * @param  value  Value.
	 * @param  op     Binary operation.
	 *
	 * @return  (This variable) <I>op</I> (<TT>value</TT>).
	 */
	public double reduce
		(double value,
		 DoubleOp op)
		{
		for (;;)
			{
			long oldvalueLong = myValue.get();
			double oldvalue = Double.longBitsToDouble (oldvalueLong);
			double newvalue = op.op (oldvalue, value);
			long newvalueLong = Double.doubleToLongBits (newvalue);
			if (myValue.compareAndSet (oldvalueLong, newvalueLong))
				{
				return newvalue;
				}
			}
		}

	/**
	 * Returns a string version of this reduction variable.
	 *
	 * @return  String version.
	 */
	public String toString()
		{
		return Double.toString (get());
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>int</TT>.
	 *
	 * @return  Current value.
	 */
	public int intValue()
		{
		return (int) get();
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>long</TT>.
	 *
	 * @return  Current value.
	 */
	public long longValue()
		{
		return (long) get();
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>float</TT>.
	 *
	 * @return  Current value.
	 */
	public float floatValue()
		{
		return (float) get();
		}

	/**
	 * Returns this reduction variable's current value converted to type
	 * <TT>double</TT>.
	 *
	 * @return  Current value.
	 */
	public double doubleValue()
		{
		return (double) get();
		}

	}